Modern electronic equipment such as televisions, telephones, radios and computers are generally constructed of solid state devices. Solid state devices are preferred in electronic equipment because they are extremely small and relatively inexpensive. Additionally, solid state devices are very reliable because they have no moving parts, but are based on the movement of charge carriers.
Solid state devices may be transistors, capacitors, resistors, and other semiconductor devices. Typically, such devices are formed in and on a substrate and are interconnected to form an integrated circuit. One type of transistor is the metal oxide semiconductor field effect transistor (MOSFET) in which current flows through a narrow conductive channel between a source and drain and is modulated by an electric field applied at the gate electrode.
The size of MOSFETs continues to be reduced to accommodate an even larger number of devices in an integrated circuit and to increase the power and capabilities of the circuit. This reduction in size leads to short channel effects that degrade device performance. Solutions such as enlarging the sidewall insulator formed along the gate electrode to space the source and drain apart from the conductive channel underlying the gate electrode have reduced short channel effects at the cost of otherwise degrading device performance. However, current semiconductor fabrication methods have not adequately reduced or eliminated these short-channel effects. In addition, degraded conductivity and leakage problems persist.